Communications and processing devices typically include cards coupled to a backplane. To perform various operations, the cards communicate data to each other using backplane buses. Because only one card may communicate data over a backplane bus at a time, the devices rely on various protocols, such as Peripheral Component Interconnect (PCI) or VersaModule Eurocard (VME), to govern communication over the bus.
Unfortunately, existing bus protocols include several functional limitations that undermine their use in conjunction with many communications applications. For example, existing bus protocols either strictly limit the number of cards that can share a bus or necessitate complex and expensive solutions to scale to a higher number of cards. Similarly, to insert or remove cards without powering down the backplane, existing protocols require cards to carry an additional chipset. In addition, existing bus protocols generally lack a mechanism for providing selective treatment to a specific stream of information among several streams sharing the same backplane bus. Without a mechanism in communications devices for prioritizing the communication of real-time packets over other types of data packets, the performance of real-time applications using real-time data streams, such as voice or video data streams, degrades appreciably. Finally, because existing bus protocols are confined to communications over a backplane bus, a communications device must use an additional protocol to communicate with external devices. For these and other readily apparent reasons, existing bus protocols increasingly limit the functionality and diminish the performance of communications devices.